Intensification of viscous fluid mixing in eccentric stirred tank systems

Zhang, Mengxue; Hu, Yinyu; Wang, Wentan; Shao, Ting; Cheng, Yi

doi:10.1016/j.cep.2013.01.006

Cited by 18 publications

(6 citation statements)

References 22 publications

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“…Further, though the calculation of mixing times using PLIF has received some attention (Busciglio et al, 2014;Hu et al, 2012;Zadghaffari et al, 2009;Zhang et al, 2013), little is available on the application of this method with viscoelastic fluids. Ozcan-Taskin & Nienow (1995) investigated flow fields and calculated mixing times for low elasticity fluids using a fibre-optic technique, additionally calculating mixing times in viscoelastic media, whilst a colorimetric method was adopted by Chhabra et al (2007).…”

Section: Figure 1: Typical Butterfly Impellermentioning

confidence: 99%

“…These geometries are almost universally employed in the blending of complex fluids, as they all possess low power draw in laminar flow. Direct torque measurement has been performed to obtain power curves in laminar flow (Fradette et al, 2007;Zhang et al, 2013;Fontaine et al, 2013), whilst flow measurements have been found using both intrusive methods such as Laser Doppler Anemometry (Jahangiri, 2007) and nonintrusive methods investigating opaque systems (Patel et al, 2014;Ihejirika and Ein-Mozaffari, 2007) and transparent varieties (Stobiac et al, 2014;Chhabra et al, 2007;Shervin et al, 1991). PIV measurements have become prevalent as the method of choice for non-intrusive determination of flow fields, owing to their non-intrusive nature and ease of application.…”

Section: Figure 1: Typical Butterfly Impellermentioning

confidence: 99%

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Mixing of Newtonian and viscoelastic fluids using “butterfly” impellers

Ramsay

Simmons

Ingram

et al. 2016

Chemical Engineering Science

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The mixing of high viscosity and viscoelastic fluids may be performed in industry using a "butterfly" impeller, which has received scant attention. This paper describes the characterisation of these impellers using both Newtonian and viscoelastic (Boger) fluids with an identical base viscosity under laminar flow conditions in batch tanks without baffles. Measurements are made using two rotational speeds (N = 30 or 60 rpm) over a wide range of impeller to tank diameter ratios from 0.53 to 0.98.Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) have been used to determine local velocity fields, shear rates, flow numbers and mixing times respectively, with impeller power number Po obtained from torque measurements. A down-pumping flow pattern is observed, with maximum normalised velocities of 25% of the impeller tip speed observed in the axial plane, increasing to 60% in the rotational plane due to solid body rotation. Angle resolved measurements found these to be slightly increased as the impeller passes the image plane, with viscoelastic fluids displaying a greater uniformity of velocity across the image planes due to elastic energy storage. Maximum shear rates are greatest between the impeller and the wall, yet remain low i.e. O (10) s -1 . Mixing times obtained from PLIF show that mixing times in viscoelastic fluids show a slight reduction compared to the Newtonian equivalent. The impeller power number was determined as Po = 0.6 in the turbulent regime, while the laminar constant K p and the Metzner-Otto constant k s were equal to 122 and 16.0 respectively. Highlights: "Butterfly" impellers used for processing of viscoelastic fluids. Low impeller Power number Po due to low blade area. Maximum shear rates of 17 s -1 in region between impeller and wall at N = 60 rpm. Mixing times longer in viscoelastic fluids due to elastic effects.

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Section: Figure 1: Typical Butterfly Impellermentioning

confidence: 99%

Section: Figure 1: Typical Butterfly Impellermentioning

confidence: 99%

Mixing of Newtonian and viscoelastic fluids using “butterfly” impellers

Ramsay

Simmons

Ingram

et al. 2016

Chemical Engineering Science

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“…This result is consistent with some previous reports that the intensification of viscous liquid mixing performance is attained in laminar or transitional regime. 8,60 For the immiscible liquid−liquid system, Rhodamine B dissolves in both aqueous and organic phases, and the mass transfer process proceeds by the interfacial contact. However, the zones at the upper/lower corner of the tank far away from the stirring shaft could not have efficient agitation to enforce the liquid−liquid dispersion.…”

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 99%

Visual Study on the Interphase Mass Transfer of Immiscible Liquid–Liquid System in a Stirred Tank

Duan

Yang

2019

Ind. Eng. Chem. Res.

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A novel experiment is designed to visually study the interphase mass transfer in an immiscible liquid–liquid system using the planar laser-induced fluorescence method combined with the refractive index matching technique. Rhodamine B is chosen as the fluorescence tracer because it can dissolve in both aqueous and organic phases. The experimental results indicate that the mass transfer equilibrium time is negatively correlated to the agitation speed. For the Rushton disk turbine, the interphase mass transfer efficiency is enhanced as the impeller clearance increases from T/10 to 2T/5. Furthermore, the interphase mass transfer process is dampened and the equilibrium time increases continuously when the volume fraction of NaI solution increases from 2 to 50%. When the impeller eccentricity increases, the mass transfer equilibrium time increases correspondingly and the trend of its change in the immiscible liquid–liquid system is contrary to that of mixing time in the single phase.

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“…Previous studies are significant, but lack of intuitive description of liquid mixing behavior and barely research on local mixing behavior in experiments. In recent years, planar laser induced fluorescence (PLIF) technique is widely used in flow visualization and quantitative measurement [18][19][20][21][22][23]. Excited by the laser light, the fluorescent agent deexcites in few nanoseconds to microseconds, and emits fluorescent at a wavelength longer than the excitation wavelength.…”

Section: Introductionmentioning

confidence: 99%

“…Since the fluorescence is generated and disappeared almost the same time with the excitation light, namely, the process is instantaneous, fluorescence intensity can be used for instantaneous measurement. Hu et al [18,19] and Zhang et al [23] have researched liquid flow field and fluorescent agent concentration in mechanical stirring reactor by PLIF technique.…”

Section: Introductionmentioning

confidence: 99%

Liquid Mixing Characteristics in Top-Blown Process

Chen

Zhang

et al. 2021

Theor Found Chem Eng

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The planar laser induced fluorescence (PLIF) technique is applied to investigate the flow and liquid mixing characteristics in submerged top-blow process. The liquid mixing effects are analyzed in terms of plane mixing uniformity U(t) and mixing time t 95 at different air flow rate and lance submergence depth. Based on experimental data, the liquid mixing process has been divided into three stages by mixing uniformity U, the beginning stage (0.9 < U < 1) , the interim stage (0.1 < U < 0.9) and the end stage (0 < U < 0.1), the value of U drops slowly in the beginning stage and the end stage, but drops rapidly in the interim stage. The mixing time t 95 is decreased obviously when increasing the air flow rate and lance submergence depth. There are significant local mixing differences in the liquid mixing process when the lance submergence depth is small. The local difference decreases evidently as the air flow rate and the lance submergence depth increase. The local differences are gradually eliminated when the lance approaches the container bottom.

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Intensification of viscous fluid mixing in eccentric stirred tank systems

Cited by 18 publications

References 22 publications

Mixing of Newtonian and viscoelastic fluids using “butterfly” impellers

Mixing of Newtonian and viscoelastic fluids using “butterfly” impellers

Visual Study on the Interphase Mass Transfer of Immiscible Liquid–Liquid System in a Stirred Tank

Liquid Mixing Characteristics in Top-Blown Process

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